At the horizon of a supersymmetric AdS_5 black hole: Isometries and half-BPS giants

The near-horizon geometry of an asymptotically AdS_5 supersymmetric black hole discovered by Gutowski and Reall is analysed. After lifting the solution to 10 dimensions, we explicitly solve the Killing spinor equations in both Poincare and global coordinates. It is found that exactly four supersymmetries are preserved which is twice the number for the full black hole. The full set of isometries is constructed and the isometry supergroup is shown to be SU(1,1|1) X SU(2) X U(3). We further study half-BPS configurations of D3-branes in the near-horizon geometry in Poincare and global coordinates. Both giant graviton probes and dual giant graviton probes are found.Comment: 26 pages. v2:Typos corrected, minor change

Activation of Epithelial-Mesenchymal Transition and Altered β-Catenin Signaling in a Novel Indian Colorectal Carcinoma Cell Line

Colorectal cancer is the third major cause of cancer-related mortality worldwide. The upward trend in incidence and mortality rates, poor sensitivity to conventional therapies and a dearth of early diagnostic parameters pose a huge challenge in the management of colorectal cancer in India. Due to the high level of genetic diversity present in the Indian population, unraveling the genetic contributions toward pathogenesis is key for understanding the etiology of colorectal cancer and in reversing this trend. We have established a novel cell line, MBC02, from an Indian colorectal cancer patient and have carried out extensive molecular characterization to unravel the pathological alterations in this cell line. In-depth molecular analysis of MBC02 revealed suppression of E-cadherin expression, concomitant with overexpression of EMT related molecules, which manifested in the form of highly migratory and invasive cells. Loss of membrane-tethered E-cadherin released β-catenin from the adherens junction resulting in its cytoplasmic and nuclear accumulation and consequently, upregulation of c-Myc. MBC02 also showed dramatic transcriptional upregulation of β-catenin. Remarkably, we observed significantly elevated proteasome activity that perhaps co-evolved to compensate for the unnaturally high mRNA level of β-catenin to regulate the increased protein load. In addition, there was substantial misregulation of other clinically relevant signaling pathways that have clinical relevance in the pathogenesis of colorectal cancer. Our findings pave the way toward understanding the molecular differences that could define pathogenesis in cancers originating in the Indian population

Calcineurin inhibitor-induced and Ras-mediated overexpression of VEGF in renal cancer cells involves mTOR through the regulation of PRAS40.

Malignancy is a major problem in patients treated with immunosuppressive agents. We have demonstrated that treatment with calcineurin inhibitors (CNIs) can induce the activation of proto-oncogenic Ras, and may promote a rapid progression of human renal cancer through the overexpression of vascular endothelial growth factor (VEGF). Interestingly, we found that CNI-induced VEGF overexpression and cancer cell proliferation was inhibited by rapamycin treatment, indicating potential involvement of the mammalian target of rapamycin (mTOR) pathway in this tumorigenic process. Here, we examined the role of mTOR pathway in mediating CNI- and Ras-induced overexpression of VEGF in human renal cancer cells (786-0 and Caki-1). We found that the knockdown of raptor (using siRNA) significantly decreased CNI-induced VEGF promoter activity as observed by promoter-luciferase assay, suggesting the role of mTOR complex1 (mTORC1) in CNI-induced VEGF transcription. It is known that mTOR becomes activated following phosphorylation of its negative regulator PRAS40, which is a part of mTORC1. We observed that CNI treatment and activation of H-Ras (through transfection of an active H-Ras plasmid) markedly increased the phosphorylation of PRAS40, and the transfection of cells using a dominant-negative plasmid of Ras, significantly decreased PRAS40 phosphorylation. Protein kinase C (PKC)-ζ and PKC-δ, which are critical intermediary signaling molecules for CNI-induced tumorigenic pathway, formed complex with PRAS40; and we found that the CNI treatment increased the complex formation between PRAS40 and PKC, particularly (PKC)-ζ. Inhibition of PKC activity using pharmacological inhibitor markedly decreased H-Ras-induced phosphorylation of PRAS40. The overexpression of PRAS40 in renal cancer cells significantly down-regulated CNI- and H-Ras-induced VEGF transcriptional activation. Finally, it was observed that CNI treatment increased the expression of phosho-PRAS40 in renal tumor tissues in vivo. Together, the phosphorylation of PRAS40 is critical for the activation of mTOR in CNI-induced VEGF overexpression and renal cancer progression

Overexpression of PRAS40 inhibits CNI- and Ras-induced VEGF transcriptional activation.

<p><i>A, top,</i> 786-0 cells were co-transfected with the 2.6-kb VEGF promoter-luciferase construct (0.5 µg/well) and either a PRAS40 overexpression plasmid (myc-PRAS40) (0.5 µg/well) or empty vector. After transfection, cells were cultured for 12 hour, and then treated overnight (12 hour) with either CsA (5.0 µg/ml) or vehicle alone (control). Following CsA treatment, cells were harvested, and fold change in luciferase activity was calculated as the relative luciferase counts from each group of cells compared with that of cells transfected with empty vector and treated with vehicle alone. <i>A, bottom,</i> The overexpression of myc-PRAS40 plasmid in transfected cells was confirmed by Western blot analysis using anti-PRAS40; and the expression of β-actin was measured as internal control. <i>B,</i> Caki-1 cells were co-transfected with the 2.6-kb VEGF promoter-luciferase construct (0.5 µg/well) and different combinations of H-Ras(12V), myc-PRAS40 and the empty vector (0.5 µg/well of each plasmid). Following 24 hour of transfection, the cells were harvested, and fold change in luciferase activity was calculated as the relative luciferase counts from each group of cells compared with that of cells transfected with empty vector. (A–B) The data reflect three independent experiments. <i>Columns,</i> average of triplicate readings of two different samples; <i>error bars,</i> SD. In A, *, <i>p</i><0.01 compared with empty vector-transfected and vehicle-treated cells; **, <i>p</i><0.01 compared with empty vector-transfected and CsA-treated cells. In B, * <i>p</i><0.01 compared with vector-transfected cells; **, <i>p</i><0.01 compared with vector- and H-Ras(12V)-transfected cells.</p

Treatment with CNI promotes the phosphorylation of PRAS40 in renal tumor tissues <i>in vivo</i>.

<p>Human renal cancer cells (1.0×10⁶; 786-0) were injected s.c. in nude (<i>nu/nu</i>) mice (<i>n</i> = 5 in each group), and they were treated either with CsA (10 mg/kg/day) or with the vehicle as control. Tumors were harvested at day 25 following tumor injection. Representative photomicrographs illustrate the immunohistochemical expression of phospho-PRAS40 (<i>top panels</i>) and PRAS40 (<i>middle panels</i>) in harvested renal tumor tissues (magnification X400). <i>Patches of dark red color,</i> expression of phosho-PRAS40, which was markedly increased in tumor tissues from CsA-treated mice. H & E, hematoxylin and eosin. Representative of three different tissue samples of both CsA- and vehicle-treated groups.</p

CNI treatment and H-Ras activation increases the phosphorylation of PRAS40.

<p><i>A,</i> The expression of phospho-PRAS40 and PRAS40 was measured in whole cell lysates of RPTEC, 786-0, and Caki-1 by Western blot analysis using anti-phospho-PRAS40 and anti-PRAS40. <i>B,</i> 786-0 cells were treated with different concentrations (1.0 and 5.0 µg/ml) of CsA or with vehicle alone (control) for 3 hour. Cells were lysed, and the expression of phospho-PRAS40 and PRAS40 was measured by Western blot analysis. <i>C,</i> Caki-1 cells were transfected with either increasing concentrations (0.1–1.0 µg/well) of H-Ras(12V) or empty expression vector (control) for 24 hour. Cells were lysed, and the expression of phospho-PRAS40, PRAS40, Ras, and β-actin in cell lysates was measured by Western blot analysis. <i>D,</i> Caki-1 cells were transfected with either different concentrations (0.5 and 1.0 µg/well) of the dominant-negative Ras(17N) or empty expression vector (control) for 24 hour. Cells were lysed, and the expression of phospho-PRAS40, and PRAS40 was measured by Western blot analysis. (A–D) Representative of three independent experiments with similar findings.</p